In communication links, often an increase in data rate aggravates the distance-dependent signal degradation in the link thereby shortening the distance that a signal can travel through the link while remaining readable. To compensate for the increased signal degradation, higher-powered transmitters and/or repeaters may be used for higher data rates, or additional repeaters may be added between existing repeaters along the link. These solutions may increase cost, complexity, power consumption, or waste heat generation.
The cost of repeaters increases by a significant fraction if they need to be configured for the particular mode of operation of each link, especially if the mode may change (e.g., one message is transmitted at a low data rate, but a subsequent message is transmitted at a higher data rate). Operating parameters that may vary between different modes of operation may include data rate, link power states, and test mode.
A re-driving repeater may receive operating parameters or configuration instructions from a sideband signal. A re-timing repeater may receive information about the mode of operation by participating in link training and detecting and decoding the communications between the two endpoints. Either approach requires significant effort. Components needing to handle high data rates reliably may be subject to more and tighter constraints than those for use at lower rates; stricter or extra constraints tend to raise production costs. In addition, the repeaters may need to track and extract their required operating parameters, e.g., a Training Sequence 1 (TS1) ordered set, from among numerous other fast-moving messages on the link. Each communication protocol may have its own identifiers tagging the ordered set. Therefore, (1) the repeater must understand the particular protocol being used by the endpoints in order to find and extract the recovery parameters, and (2) a change in protocol on a network may involve replacing (or at least reconfiguring) all the affected repeaters. Both of these constraints also add cost.
The cost, energy efficiency, and reliability of PCIe and similar networks could therefore benefit from a way to make the repeaters simpler or to make them more versatile to use for different protocols. The present disclosure addresses such needs.